Interobserver agreement in MRI assessment of severity of placenta accreta spectrum disorders.

OBJECTIVE: To evaluate the level of agreement in the prenatal magnetic resonance imaging (MRI) assessment of the presence and severity of placenta accreta spectrum (PAS) disorders between examiners with expertise in the diagnosis and management of these conditions. METHODS: This was a secondary analysis of a prospective study including women with placenta previa or low-lying placenta and at least one prior Cesarean delivery or uterine surgery, who underwent MRI assessment at a regional referral center for PAS disorders in Italy, between 2007 and 2017. The MRI scans were retrieved from the hospital electronic database and assessed by four examiners, who are considered to be experts in the diagnosis and surgical management of PAS disorders. The examiners were blinded to the ultrasound diagnosis, histopathological findings and clinical data of the patients. Each examiner was asked to assess 20 features on the MRI scans, including the presence, depth and topography of placental invasion. Depth of invasion was defined as the degree of adhesion and invasion of the placenta into the myometrium and uterine serosa (placenta accreta, increta or percreta) and the histopathological examination of the removed uterus was considered the reference standard. Topography of the placental invasion was defined as the site of placental invasion within the uterus in relation to the posterior bladder wall (posterior upper bladder wall and uterine body, posterior lower bladder wall and lower uterine segment and cervix or no visible bladder invasion) and the site of invasion at surgery was considered the reference standard. The degree of interrater agreement (IRA) was evaluated by calculating both the percentage of observed agreement among raters and the Fleiss kappa (κ) value. RESULTS: Forty-six women were included in the study. The median gestational age at MRI was 33.8 (interquartile range, 33.1-34.0) weeks. A final diagnosis of placenta accreta, increta and percreta was made in 15.2%, 17.4% and 50.0% patients, respectively. There was excellent agreement between the four examiners in the assessment of the overall presence of a PAS disorder (IRA, 92.1% (95% CI, 86.8-94.0%); κ, 0.90 (95% CI, 0.89-1.00)). However, there was significant heterogeneity in IRA when assessing the different MRI signs suggestive of a PAS disorder. There was excellent agreement between the examiners in the identification of the depth of placental invasion on MRI (IRA, 98.9% (95% CI, 96.8-100.0%); κ, 0.95 (95% CI, 0.89-1.00)). However, agreement in assessing the topography of placental invasion was only moderate (IRA, 72.8% (95% CI, 72.7-72.9%); κ, 0.56 (95% CI, 0.54-0.66)). More importantly, when assessing parametrial invasion, which is one of the most significant prognostic factors in women affected by PAS, the agreement was substantial and moderate in judging the presence of invasion in the coronal (IRA, 86.6% (95% CI, 86.5-86.7%); κ, 0.69 (95% CI, 0.59-0.71)) and axial (IRA, 78.6% (95% CI, 78.5-78.7%); κ, 0.56 (95% CI, 0.33-0.60)) planes, respectively. Likewise, interobserver agreement in judging the presence and the number of newly formed vessels in the parametrial tissue was moderate (IRA, 88.0% (95% CI, 88.0-88.1%); κ, 0.59 (95% CI, 0.45-0.68)) and fair (IRA, 66.7% (95% CI, 66.6-66.7%); κ, 0.22 (95% CI, 0.12-0.37)), respectively. CONCLUSIONS: MRI has excellent interobserver agreement in detecting the presence and depth of placental invasion, while agreement between the examiners is lower when assessing the topography of invasion. The findings of this study highlight the need for a standardized MRI staging system for PAS disorders, in order to facilitate objective correlation between prenatal imaging, pregnancy outcome and surgical management of these patients. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Diagnostic accuracy of first-trimester ultrasound in detecting abnormally invasive placenta in high-risk women with placenta previa.

OBJECTIVE: To ascertain the diagnostic accuracy of ultrasound in detecting abnormally invasive placenta (AIP) during the first trimester of pregnancy (11-14 weeks' gestation) in women at risk for this condition. METHODS: This was a retrospective analysis of data collected prospectively from women at risk for AIP based upon the presence of at least one prior Cesarean section (CS) and/or uterine surgery and placenta previa, who had ultrasound assessment for AIP at the time of the 11-14-week scan. The ultrasound signs explored in the present study were: loss of the clear zone, placental lacunae, bladder wall interruption and uterovesical hypervascularity. The potential of ultrasound and different ultrasound signs to predict the different types of AIP was assessed by computing summary estimates of sensitivity, specificity, diagnostic odds ratio (DOR) and positive (LR+) and negative (LR-) likelihood ratios. RESULTS: One hundred and eighty-eight women with placenta previa and at least one previous CS or uterine surgery were included in the study. All the explored ultrasound signs were associated significantly with the occurrence of AIP. Overall, when at least one ultrasound sign was used to make the diagnosis, ultrasound had a sensitivity of 84.3% (95% CI, 74.7-91.4%), specificity of 61.9% (95% CI, 51.9-71.2%), DOR of 8.6 (95% CI, 4.1-19.3), LR+ of 2.2 (95% CI, 1.7-2.9) and LR- of 0.3 (95% CI, 0.1-0.4) in detecting AIP. Using two ultrasound signs to label a case as positive increased the diagnostic accuracy in terms of specificity, although it did not affect sensitivity. Among the different ultrasound signs, loss of the clear zone had a sensitivity of 84.3% (95% CI, 74.7-91.4%) and a specificity of 81.9% (95% CI, 73.2-88.7%) in detecting AIP, while sensitivities for placental lacunae and bladder wall interruption were 78.3% (95% CI, 67.9-86.6%) and 75.9% (95% CI, 65.3-84.6%), respectively, and specificities were 81.0% (95% CI, 72.1-88.0%) and 99.1% (95% CI, 94.8-100.0%), respectively. The optimal combination of sensitivity and specificity was achieved when at least two imaging signs of AIP were used in the diagnostic algorithm. CONCLUSIONS: AIP can be detected from the first trimester of pregnancy in women at risk for this condition, and ultrasound performed between 11 and 14 weeks' gestation has an overall good diagnostic accuracy for detecting all types of AIP. However, these findings are applicable only to women with placenta previa and prior uterine scar. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

First-trimester prediction of surgical outcome in abnormally invasive placenta using the cross-over sign.

OBJECTIVE: Ultrasound assessment of the relationship between the ectopic gestational sac and the endometrial line (cross-over sign; COS) in Cesarean scar pregnancy (CSP) has been shown to be useful in predicting the evolution of CSP towards different types of abnormally invasive placenta (AIP). The aim of this study was to ascertain whether the COS can be used to predict surgical outcome in women with AIP. METHODS: A retrospective analysis was performed of early first-trimester (6-8 weeks' gestation) ultrasound images of women with AIP managed in the third trimester of pregnancy. We hypothesized that assessment of COS may identify cases of AIP at higher risk of intra- or postsurgical morbidity. Outcomes explored were estimated blood loss during surgery, need for and amount of packed red blood cells and fresh frozen plasma units required either during or after surgery, operative time, intrasurgical complications, gestational age at birth, delivery < 34 weeks of gestation, length of hospital stay and admission to intensive care unit. Differences in the explored outcomes were assessed among women with different types of COS variant (COS-1, COS-2+ or COS-2-) as observed on first-trimester ultrasound examination. RESULTS: Sixty-eight pregnancies were included in the study. Mean estimated blood loss was higher in AIP pregnancies with COS-1 than in those with COS-2+ (P = 0.039) or COS-2- (P = 0.01). Mean number of packed red blood cell units required during or after the operation was higher in women with COS-1 compared with those with COS-2+ (P = 0.001) and COS-2- (P = 0.029), while there was no difference between pregnancies with COS-2+ and those with COS-2- (P = 0.797). Mean operative time was longer in AIP pregnancies with COS-1 than in those with COS-2+ (P = 0.039) or COS-2- (P = 0.017). Finally, pregnancies with COS-1 were delivered earlier than those with COS-2+ (P = 0.0001) or COS-2- (P = 0.0001). CONCLUSION: First-trimester ultrasound assessment of the relationship between the ectopic gestational sac and the endometrial line (COS) may identify women with AIP who are at higher risk of intra- or postsurgical morbidity. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

First-trimester detection of abnormally invasive placenta in high-risk women: systematic review and meta-analysis.

OBJECTIVES: The primary aim of this systematic review was to ascertain whether ultrasound signs suggestive of abnormally invasive placenta (AIP) are present in the first trimester of pregnancy. Secondary aims were to ascertain the strength of association and the predictive accuracy of such signs in detecting AIP in the first trimester. METHODS: An electronic search of MEDLINE, EMBASE, CINAHL and Cochrane databases (2000-2016) was performed. Only studies reporting on first-trimester diagnosis of AIP that was subsequently confirmed in the third trimester either during operative delivery or by pathological examination were included. Meta-analysis of proportions, random-effects meta-analysis and hierarchical summary receiver-operating characteristics curve analysis were used to analyze the data. RESULTS: Seven studies, involving 551 pregnancies at high risk of AIP, were included. At least one ultrasound sign suggestive of AIP was detected in 91.4% (95% CI, 85.8-95.7%) of cases with confirmed AIP. The most common ultrasound feature in the first trimester of pregnancy was low implantation of the gestational sac close to a previous uterine scar, which was observed in 82.4% (95% CI, 46.6-99.8%) of cases. Anechoic spaces within the placental mass (lacunae) were observed in 46.0% (95% CI, 10.9-83.7%) and a reduced myometrial thickness in 66.8% (95% CI, 45.2-85.2%) of cases affected by AIP. Pregnancies with a low implantation of the gestational sac had a significantly higher risk of AIP (odds ratio, 19.6 (95% CI, 6.7-57.3)), with a sensitivity and specificity of 44.4% (95% CI, 21.5-69.2%) and 93.4% (95% CI, 90.5-95.7%), respectively. CONCLUSIONS: Ultrasound signs of AIP can be present during the first trimester of pregnancy, even before 11 weeks' gestation. Low anterior implantation of the placenta/gestational sac close to or within the scar was the most commonly seen early ultrasound sign suggestive of AIP, although its individual predictive accuracy was not high. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Natural history of Cesarean scar pregnancy on prenatal ultrasound: the crossover sign.

OBJECTIVE: Advances in prenatal imaging techniques have led to an increase in the diagnosis of Cesarean scar pregnancy (CSP). However, antenatal counseling when CSP is diagnosed is challenging, and current evidence is derived mainly from small series reporting high rates of adverse maternal outcomes. The aim of this study was to ascertain the performance of prenatal ultrasound in predicting the natural history of CSP using a new sonographic sign, the crossover sign (COS). METHODS: This was a retrospective analysis of early first-trimester (6-8 weeks' gestation) ultrasound images in women with morbidly adherent placenta (MAP) managed in the third trimester of pregnancy. The relationship between the gestational sac of the CSP, anterior uterine wall and Cesarean scar, defined as the COS, was analyzed to determine whether it could predict evolution in these cases. Odds ratios (ORs) were calculated and logistic regression analysis was performed to investigate the association between different types of COS (COS-1, COS-2+ or COS-2-) and the occurrence of MAP. RESULTS: Sixty-eight pregnancies with MAP were included. The risk of placenta percreta was significantly higher in pregnancies with COS-1 than in those with COS-2 (OR, 6.67 (95% CI, 1.3-33.3)). When evaluating the two variants of COS-2 separately, the risk of placenta percreta was significantly higher in pregnancies with COS-1 vs COS-2+ (OR, 5.83 (95% CI, 1.1-30.2)) and this risk was even higher when comparing cases with COS-1 vs COS-2- (OR, 12.0 (95% CI, 1.9-75.7)). Logistic regression analysis showed that COS-1 was associated independently with severe forms of MAP, such as placenta percreta and increta (OR, 12.85 (95% CI, 2.0-84.0)), while COS-2+ was associated independently with placenta accreta (OR, 4.37 (95% CI, 1.1-17.0)). CONCLUSIONS: Ultrasound assessment of the relationship between the gestational sac of a CSP and the endometrial line (the COS) may help to determine whether a CSP will progress towards a less severe form of MAP, amenable to postnatal treatment, and successful pregnancy outcome. Large prospective studies are needed to confirm our findings and elucidate the natural history of this condition. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.